Ultrasonic study of molecular association of poly(vinyl chloride) solution in tetrahydrofuran

Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules.     

基于AOTF的在线红外光谱测量系统

介绍了一种新型的红外光谱测量系统，它由准直发射系统和聚焦接收系统两大部分组成，以声光可调谐滤光器（AOTF）为色散元件，连续改变AOTF的驱动频率就能实现快速波长扫描，达到实时测量目的。该系统具有结构简单、测量快速等特点，可用于在线有害气体检测和红外光谱分析。实验表明，系统光谱测量范围2．5－5μm，光谱分辨力为10nm。     

缺陷交互作用对陶瓷半导体导电性能的影响

本文借助于缺陷化学反应过程，分析了陶瓷半导体内缺陷间的交互作用，得到了陶瓷半导体实验研究的三个重要启示：（1）强还原（或氧化）或施主（或受主）掺杂对同一样品不能同时起到最佳效果；（2）本征原子空位对施主或受主的补偿导致电导率的非线性增长；（3）缺陷的缔合降低了半导化杂质的有效浓度，从而使电导性能发生异常变化。     

Automated Support for Building and Extending Expert Models

Building a knowledge-based system is like developing a scientific theory. Although a knowledge base does not constitute a theory of some natural phenomenon, it does represent a theory of how a class of professionals approaches an application task. As when scientists develop a natural theory, builders of expert systems first must formulate a model of the behavior that they wish to understand and then must corroborate and extend that model with the aid of specific examples. Thus there are two interrelated phases of knowledge-base construction: (1) model building and (2) model extension. Computer-based tools can assist developers with both phases of the knowledge-acquisition process. Workers in the area of knowledge acquisition have developed computer-based tools that emphasize either the building of new models or the extension of existing models. The PROTÉGÉ knowledge-acquisition system addresses these two activities individually and facilitates the construction of expert systems when the same general model can be applied to a variety of application tasks.     

High temperature low cycle fatigue

Fatigue at high temperature is a complex phenomenon as it is influenced by a number of time-dependent processes which become important at elevated temperatures. These processes include creep, oxidation, phase instabilities and dynamic strain ageing (DSA), acting either independently or synergistically influence fatigue behaviour, often lowering the fatigue life. Current design approaches employ linear summation of fatigue and creep damage with suitable factors on permissible damage to take care of uncertainties in interaction between cyclic and time-dependent processes. It is, therefore, important to develop a deeper understanding of the processes that occur during high temperature fatigue so that realistic life predictions could be made. Results on the high temperature fatigue behaviour of austenitic stainless steels, ferritic steels and nickel base alloys are presented here. The important mechanisms of interaction of high temperature time-dependent processes with fatigue under various conditions are discussed in detail. Emphasis is placed on cyclic stress response, fatigue life, deformation substructure and fracture behaviour. This is followed by a review of important life prediction techniques under combined creep-fatigue loading conditions. Life prediction techniques considered here include linear damage summation, strain range partitioning, ductility exhaustion approach, frequency modified and frequency separation methods, techniques based on hysteresis energy and damage rate models, and methods based on crack-cavitation interation models.     

严格环境管理提高环境意识

环境伴随着经济的发展越来越体现了它的重要性,全社会应重视环境、保护环境,以预防为主,加强综合治理,使我们的天更蓝、水更净、草更绿,到处充满着春的意境.     

A simple correlation for estimating viscosities of solutions of salts in aqueous,non-aqueous and mixed solvents applicable to high concentration,temperature and pressure

A new correlation is proposed to correlate the viscosities of salt solutions in aqueous, non-aqueous solvents and their mixtures. The correlation involves two parameters i.e. solvation number and ion-solvent interaction coefficient, which are well-documented quantities in the literature. The proposed correlation has been examined on the experimental viscosity data of salt solutions in aqueous, non-aqueous and their mixtures up to 473 K and 31 MPa pressure. The salts with various ionic charges were employed for testing the proposed correlation. Several non-aqueous solvents like dimethyl sulphoxide, alcohols and formamide were included for the data regression. The viscosities of these solutions can be correlated to within 0.7%.     

地基基础与上部结构共同作用和结构次生应力问题

本文考虑到上部结构与地基基础共同作用的事实,着重分析上部结构参与共同作用导致的内力重分布——次生应力问题。通过多个理论与实验的结果,对不同地基和基础条件下的次生应力进行了定量分析,探讨了造成次生应力的各种因素以及对建筑结构带来的危害。     

用频谱分析法对地下水位进行中长期预报

本文把影响地下水位变化过程作为随机过程，用频谱分析法建立随机水动力学模型模拟地下水位的变化过程，并将其用于地下水位的中长期预报。通过实例验证它具有较高的精度。     

离聚物对PET／LDPE共混物的结构与性能研究

用双螺杆挤出机反应性挤出的方法合成了低密度聚乙烯接枝马来酸镧（ＬＤＰＥ－ｇ－ＭＡＬａ）离聚物。与其它方法相比，该法具有工艺简单，易于工业化生产的特点。我们将离聚物与ＰＥＴ，ＬＤＰＥ在双螺杆挤出机上熔融共混挤出，并用注射成型机制备标准样条，对共混物力学性能进行了测试，发现离聚物有显著的增韧效果，另外，通过ＩＲ，ＤＳＣ，溶解性实验，分子量的测定等还考察了离聚物对ＰＥＴ／ＬＤＰＥ共混体系的结构影响。